从XDocument检索XML元素的序列

Question

I have a sample xml as follows

<users>
  <user>
    <username>John</username>
    <password>password1</password>
    <id>1234</id>
  </user>
  <user>
    <username>Smith</username>
    <password>password2</password>
    <id>1234</id>
  </user>       
<users>

This XML file is loaded into XDocument object like this..

XDocument xDoc = XDocument.Load("Users.xml");

How can I retrieve values of password and id elements by passing username as a parameter to it where username is unique in c#.net 4.0

Answer 1

You can try the following code snippet (method) to extract the password from Xml doc by passing UserName as parameter:

public string GetUserPassword(string UserName)
{
    XDocument xDoc = XDocument.Load("Users.xml");
    XmlNodeList _users = xDoc.SelectNodes("//users/user");
    string _pwd = null;
    foreach (XmlNode _node in _users)
    {
        if (_node.SelectSingleNode("username").InnerText == UserName)
        {
            _pwd = _node.SelectSingleNode("password").InnerText;
            break;
        }
    }
    return _pwd;
}

And, similar one to get the id :

public string GetId(string UserName)
{
    XDocument xDoc = XDocument.Load("Users.xml");
    XmlNodeList _users = xDoc.SelectNodes("//users/user");
    string _id = null;
    foreach (XmlNode _node in _users)
    {
        if (_node.SelectSingleNode("username").InnerText == UserName)
        {
            _id = _node.SelectSingleNode("id").InnerText;
            break;
        }
    }
    return _id;
}

For performance optimization you can combine this two methods into one, so the Xml document will be loaded just once while method will return the array string[] _pwdAndId , where _pwdAndId[0] corresponds to the id and _pwdAndId[1] to password.

public string[] GetPasswordAndId(string UserName)
{
    XDocument xDoc = XDocument.Load("Users.xml");
    XmlNodeList _users = xDoc.SelectNodes("//users/user");
    string[] _pwdAndId = new string[2];
    foreach (XmlNode _node in _users)
    {
        if (_node.SelectSingleNode("username").InnerText == UserName)
        {
            _pwdAndId[0] = _node.SelectSingleNode("id").InnerText;
            _pwdAndId[1] = _node.SelectSingleNode("password").InnerText;
            break;
        }
    }
    return _pwdAndId ;
}

Hope this will help. Best regards,